Those who did their own readings at home and adjusted medicine as needed had healthier blood pressure levels after a year than those who got standard doctors' care.

Self-care patients weren't completely on their own - any changes they made were part of a treatment plan previously OK'd by their doctors. But the patients didn't need to consult their doctors every time they increased the dose if it was part of the original treatment plan.

Why self-management worked best is uncertain, but patients who participated were taking more medication than the others and were perhaps more vigilant than doctors treating the usual-care group.

It's possible that the doctors had "clinical inertia" - a phenomenon in which physicians often fail to adjust blood pressure medication even when patients' levels are too high, said study author Richard McManus, a professor at the University of Oxford.The study was published Tuesday in the Journal of the American Medical Association.

Nearly 1 in 3 U.S. adults have high blood pressure - measuring 140 over 90 or higher - but only about half of them have it adequately controlled, according to the Centers for Disease Control and Prevention. High blood pressure rates are similar in England, health surveys there have found.

The study involved 450 patients with previous heart trouble, strokes, diabetes or kidney disease, aged 70 on average, who were followed for a year. About half got usual care; the others did self-care.